Sulfur Vacancies In Photorefractive Sn2P2S6 Crystals,
2014
Air Force Institute of Technology
Sulfur Vacancies In Photorefractive Sn2P2S6 Crystals, Eric M. Golden, Sergey A. Basun, A. A. Grabar, I. M. Stoika, Nancy C. Giles, D. R. Evans, Larry E. Halliburton
Faculty Publications
A photoinduced electron paramagnetic resonance (EPR) spectrum in single crystals of Sn2P2S6 (SPS) is assigned to an electron trapped at a sulfur vacancy. These vacancies are unintentionally present in undoped SPS crystals and are expected to play an important role in the photorefractive behavior of the material. Nonparamagnetic sulfur vacancies are formed during the initial growth of the crystal. Subsequent illumination below 100 K with 442 nm laser light easily converts these vacancies to EPR-active defects. The resulting S = 1/2 spectrum shows well-resolved and nearly isotropic hyperfine interactions with two P ions and two Sn ions. Partially resolved interactions …
A Study Of Energy Resolution And Non-Proportionality Of Yalo3:Ce And Gd3ga3al2o12:Ce,
2014
University of Tennessee - Knoxville
A Study Of Energy Resolution And Non-Proportionality Of Yalo3:Ce And Gd3ga3al2o12:Ce, Samuel Bradley Donnald
Doctoral Dissertations
For many radiation detection applications, energy resolution is one of the most important detector characteristics. In well designed scintillation detectors, the energy resolution is primarily driven by two main factors - the light output and light yield non-proportionality. A great deal of research has already focused on understanding and improving the light yield of scintillation detectors; however, light yield non-proportionality is less well understood. Until recently, light yield non-proportionality was thought to be an intrinsic scintillator property with very little sample-to-sample variation. In this work, two materials have been investigated that demonstrate a variable light yield non-proportionality. The first material …
Performance Analysis Of A Hybrid Raman Optical Parametric Amplifier In The O- And E-Bands For Cwdm Pons,
2014
CUNY City College
Performance Analysis Of A Hybrid Raman Optical Parametric Amplifier In The O- And E-Bands For Cwdm Pons, Sasanthi Peiris, Nicolas Madamopoulos, Neophytos A. Antoniades, Dwight Richards, Roger Dorsinville
Publications and Research
We describe a hybrid Raman-optical parametric amplifier (HROPA) operating at the O- and E-bands and designed for coarse wavelength division multiplexed (CWDM) passive optical networks (PONs). We present the mathematical model and simulation results for the optimization of this HROPA design. Our analysis shows that separating the two amplification processes allows for optimization of each one separately, e.g., proper selection of pump optical powers and wavelengths to achieve maximum gain bandwidth and low gain ripple. Furthermore, we show that the proper design of optical filters incorporated in the HROPA architecture can suppress idlers generated during the OPA process, as well …
Gesn Light-Emitting Devices,
2014
University of Arkansas, Fayetteville
Gesn Light-Emitting Devices, Yiyin Zhou
Graduate Theses and Dissertations
Silicon based optoelectronic devices have been investigated for decades. However, due to the indirect band gap nature of Si and Ge, developing of efficient light-emitting source on Si is still a challenging topic. GeSn based optoelectronic devices have the great potential to overcome this deficiency for several reasons. By adding more fraction of Sn into Ge, GeSn band gap could be reduced. The narrowed band gap could be developed for near to mid infrared applications. The alloy can even become the direct band gap material with a large Sn composition (beyond 8%). This feature could enhance the light emission from …
Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings,
2014
University of Arkansas, Fayetteville
Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson
Graduate Theses and Dissertations
Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective …
Zone Refining Of Raw Materials For Metal Halide Scintillator Crystal Growth,
2014
University of Tennessee - Knoxville
Zone Refining Of Raw Materials For Metal Halide Scintillator Crystal Growth, Thomas Williams Mcalexander
Masters Theses
In recent years, scintillators have been researched for homeland security applications where properties such as high light output and low energy resolution are required for efficient gamma ray spectroscopy. Several promising scintillators, including SrI2 [Strontium Iodide], CsSrI3 [Cesium Strontium Iodide], and KSr2I5 [Potassium Strontium Iodide] are activated with EuI2 [Europium Iodide]. The quality of EuI2 raw material is generally poor and inconsistent as-received from the manufacturer. Material purity is known to affect its scintillation performance, and so purification processes have been investigated to improve the performance of Eu-doped [Europium-doped] scintillators. In this …
Engineering Surface Functionality Of Nanoparticles For Biological Applications,
2014
University of Massachusetts Amherst
Engineering Surface Functionality Of Nanoparticles For Biological Applications, Yi-Cheun Yeh
Doctoral Dissertations
Engineering the surface functionality of nanomaterials is the key to investigate the interactions between nanomaterials and biomolecules for potent biological applications such as therapy, imaging and diagnostics. My research has been orientted to engineer both of the surface monolayers and core materials to fabricate surface-functionalized nanomaterials through the synergistic multidisciplinary approach that combine organic chemistry, materials science and biology. This thesis illustrates the design and synthesis of the surface-funcitonalized quantum dots (QDs) and gold nanoparticles (AuNPs) for the fundamental studies and practical applications. For QDs, A new class of cationic QDs with quaternary ammonium derivatives was synthesized to provide permanent …
Development Of A High Precision Quantum Dot Synthesis Method Utilizing A Microfluidic Reactor And In-Line Fluorescence Flow Cell,
2014
California Polytechnic State University, San Luis Obispo
Development Of A High Precision Quantum Dot Synthesis Method Utilizing A Microfluidic Reactor And In-Line Fluorescence Flow Cell, William Henry Lafferty
Master's Theses
Quantum dots show great potential for use as spectral converters in solar cells, lighting applications, and biological imaging. These applications require precise control of quantum dot size to maximize performance. The quality, size, and fluorescence of quantum dots depend on parameters that are difficult to control using traditional batch synthesis processes. An alternative, high precision process was developed for the synthesis of cadmium-selenide quantum dots using a microfluidic reactor and fluorescence flow cell. The process required creating separate cadmium and selenium precursors that were then mixed in a nitrogen environment at 17°C. Using an NE-300® syringe pump, the solution …
Electrochemically Active Biofilm Assisted Synthesis Of Ag@Ceo2 Nanocomposites For Antimicrobial Activity, Photocatalysis And Photoelectrodes,
2014
Universiti Brunei Darussalaam
Electrochemically Active Biofilm Assisted Synthesis Of Ag@Ceo2 Nanocomposites For Antimicrobial Activity, Photocatalysis And Photoelectrodes, Mohammad Mansoob Khan Dr, S. A. Ansari, J. H. Lee, M. O. Ansari, J Lee, M. H. Cho
Dr. Mohammad Mansoob Khan
Ag@CeO2 nanocomposites were synthesized by a biogenic and green approach using electrochemically active biofilms (EABs) as a reducing tool. The as-synthesized Ag@CeO2 nanocomposites were characterized and used in antimicrobial, visible light photocatalytic and photoelectrode studies. The Ag@CeO2 nanocomposites showed effective and efficient bactericidal activities and survival test against Escherichia coli O157:H7, and Pseudomonas aeruginosa. The as-synthesized Ag@CeO2 nanocomposites also exhibited enhanced visible light photocatalytic degradation of 4-nitrophenol and methylene blue than pure CeO2. A photocatalytic investigation showed that the Ag@CeO2 nanocomposites possessed excellent visible light photocatalytic activities compared to pure CeO2. Electrochemical impedance spectroscopy and photocurrent measurements showed that the …
Molecular Engineering Strategies For The Design And Synthesis Of New Organic Photovoltaic Materials,
2014
University of Massachusetts Amherst
Molecular Engineering Strategies For The Design And Synthesis Of New Organic Photovoltaic Materials, Paul J. Homnick
Doctoral Dissertations
Dramatic improvements in organic photovoltaic device efficiency can be obtained by optimizing spectral absorbance and frontier molecular orbital (FMO) energies, increasing solid state exciton/charge mobility, and utilizing p-/n-type nanoarchitecture. Combining all of these properties into a new material presents a considerable synthetic challenge because potential commercial applications require materials that are high-performance and inexpensive. Thus, it is advantageous to design new materials using a versatile, modular synthetic approach that allows each design criterion to be engineered individually, in a synthetically efficient manner. Several strategies were successfully pursued using simple interchangeable electron donor and acceptor components as functional modules, which …
Investigation Of The Dynamics Of Photocarriers During Photoelectrochemical Water Splitting By Combination Of Photoelectrochemistry And Transient Absorption Spectroscopy,
2014
Department of Chemistry, Zhejiang University, Hangzhou 310027, China;
Investigation Of The Dynamics Of Photocarriers During Photoelectrochemical Water Splitting By Combination Of Photoelectrochemistry And Transient Absorption Spectroscopy, Wen-Hua Leng
Journal of Electrochemistry
Semiconductor photoelectrochemical hydrogen production is an important and promising technology for utilizing solar energy. The efficiency of hydrogen production depends on the efficiencies of separation and transport of photo-generated carriers. A deep understanding of the behavior of these processes has guiding significance for designing efficient solar hydrogen device. photoelectrochemical and transient absorption spectroscopy methods are powerful tool for studying the microscopic dynamics and mechanism of photocatalytic reaction. This review describes the part of the latest results of the author regarding the semiconductor photoelectrochemical hydrogen production obtained by these methods，and the problems and future research priorities in this field are proposed.
Effects Of Thermal Boundary Conditions During Finite Element Modeling Of Physical Vapor Transport,
2014
Minnesota State University, Mankato
Effects Of Thermal Boundary Conditions During Finite Element Modeling Of Physical Vapor Transport, Wade Luhman
Journal of Undergraduate Research at Minnesota State University, Mankato
Physical vapor transport (PVT) is a material processing method commonly used to produce different types of semiconductor materials. Computer modeling of PVT is important to understand the fundamentals of the processing method. Due to the large amount of computer processing power and storage needed to solve the computer models many of the previously solved simulations have been simplified to efficiently utilize computer usage. Previous PVT computer simulations of mercurous chloride (Hg2Cl2) have assumed constant temperature profiles on the source and crystal substrate for simplicity. These simulations were performed using the FIDAP computational fluid dynamics software package. In this research the …
Single Cuo Nanowires Electrical Properties And Application On Photoelectrochemical Water Splitting,
2014
Washington University in St Louis
Single Cuo Nanowires Electrical Properties And Application On Photoelectrochemical Water Splitting, Junnan Wu
McKelvey School of Engineering Theses & Dissertations
Charge transport in single crystal, p type copper oxide (CuO) nanowires (NWs) was studied through temperature based (120 K – 400 K) current-voltage (I-V) measurements of 2-terminal single NW devices. Individual CuO NWs with an average diameter of 220 nm were attached to Au electrodes 2.5 µm apart, using a dielectrophoresis method. I-V curves showed a transition from linear behavior at low bias to strong power law dependence (I ~ Va) at high bias, which can be attributed to space charge limited current (SCLC) mechanism. At low electrical fields (< 0.89 × 103 V·cm-1), the number of …
Three Dimensional Transient Asymmetric Flowfields In Physical Vapor Transport,
2014
Minnesota State University, Mankato
Three Dimensional Transient Asymmetric Flowfields In Physical Vapor Transport, Joseph Dobmeier
Journal of Undergraduate Research at Minnesota State University, Mankato
Physical Vapor Transport is a manufacturing process used to produce single crystals of semiconductor materials such as mercurous chloride (Hg2Cl2). In the past this time-varying process has been studied with numerical simulation by considering three dimensional flow using an axi-symmetric two dimensional model or by restricting the simulation to asymmetric two dimensional flow and dropping the assumption of axi-symmetry from the model. It is generally agreed that neither of these methods accurately represent the true behavior of the process. The purpose of this research was to extend the asymmetric two dimensional model to three dimensions thereby obtaining a solution which …
Micro-Mechanics Simulation Tool Optimization,
2014
Purdue University
Micro-Mechanics Simulation Tool Optimization, Ruixuan Ren, Marisol Koslowski
The Summer Undergraduate Research Fellowship (SURF) Symposium
Crystalline films grown epitaxially on substrates consisting of a different crystalline material are of considerable interest in optoelectronic devices and the semiconductor industry. One way to progress in this field is to develop simulation tools based on specially designed numerical method. A nanoHUB simulation tool was developed based on the phase field theory, which considers the propagation of dislocations inside the crystalline film. However, the current tool needs several improvements to be more realistic and user-friendly. First, the inputs of the simulation tool are adjusted so that the user can use this tool directly without any additional calculation. The output …
Polymer-Based Thermoelectric Devices,
2014
Purdue University
Polymer-Based Thermoelectric Devices, Stuart W. Hilsmier, Edward P. Tomlinson, Bryan Boudouris
The Summer Undergraduate Research Fellowship (SURF) Symposium
Currently, over 50% of all energy generated in the US is lost as waste heat, and thermoelectric generators offer a promising means to recoup some of this energy, if their efficiency is improved. While organic thermoelectric materials lack the efficiency of their inorganic counterparts, they are composed of highly abundant resources and have low temperature processing conditions. Recently, a new class of redox-active polymers, radical polymers, has exhibited high electrical conductivity in an entirely amorphous medium. In addition, these radical polymers have a simple synthetic scheme and can be highly tunable to provide desired electrical properties. In this study, the …
Development Of A Nanomanufacturing Process To Produce Atomically Thin Black Phosphorus,
2014
Bradley University
Development Of A Nanomanufacturing Process To Produce Atomically Thin Black Phosphorus, Andrew Stephens, Zhe Luo, Xianfan Xu
The Summer Undergraduate Research Fellowship (SURF) Symposium
Atomically thin black phosphorus (phosphorene) has both unique and desirable properties that differ from bulk black phosphorus. Unlike graphene, phosphorene has a bandgap, which makes it potentially useful for applications in the next generation of transistors. Large-scale applications of phosphorene, like other 2D materials, are limited by current production methods. The most common method of making phosphorene is mechanical exfoliation, which can only produce small and irregular quantities. In this work we investigate a top-down method of producing phosphorene by using a scanning ultrafast laser to thin black phosphorus flakes. Because the bandgap of phosphorene increases as layers are removed, …
Implementing The ‘Frozen Potential’ Approach On Adept To Analyze Thin Film Solar Cells,
2014
Purdue University
Implementing The ‘Frozen Potential’ Approach On Adept To Analyze Thin Film Solar Cells, Abhirit Kanti, Raghu Vamsi Krishna Chavali, Mark S. Lundstrom Phd, Muhammad A. Alam Phd
The Summer Undergraduate Research Fellowship (SURF) Symposium
Thin film solar cells have higher absorption coefficients than traditional Silicon solar cells. This means that lesser material is required to produce the same power output for a given intensity of solar illumination. As a result, they are less expensive, easier to install and have a wider range of applications. Analyzing the performance of cells requires separating the current into the photocurrent and the injection current based on the ‘Superposition Principle’. For thin film solar cells, this cannot be done using the conventional method. This is because these components are interdependent, and so modeling one’s behavior requires understanding the other. …
Development Of A Silicon Nanowire Mask Using Scanning Probe Microscopy,
2014
California Polytechnic State University, San Luis Obispo
Development Of A Silicon Nanowire Mask Using Scanning Probe Microscopy, Ross Gregoriev
Master's Theses
Scanning probe microscopy techniques were used to investigate the desorption of hydrogen passivated silicon to form SiO2 etch masks The application of the etch masks were planned on being used to manufacture silicon nanowires. Low concentration hydrofluoric acid was used to passivate the surface. The surface was selectively depassivated by SPM techniques. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) were used to create the masks. The STM system used was found to desorb hydrogen from the surface faster than the STM could image and was considered incapable in the configuration investigated. This led to the use of atomic …
Effects Of Nanoholes Grown By Molecular Beam Droplet Epitaxy On Electrical Properties Of Two Dimensional Electron Gas,
2014
University of Arkansas, Fayetteville
Effects Of Nanoholes Grown By Molecular Beam Droplet Epitaxy On Electrical Properties Of Two Dimensional Electron Gas, Yusuke Hirono
Graduate Theses and Dissertations
The effects of nanoholes, grown by molecular beam droplet epitaxy, on the electrical properties of quantum well (QW) heterostructures are reported. To investigate how the depth of nanoholes affect the electrical properties of the QW heterostructures, the growth conditions for nanoholes were optimized with respect to their depth and density. Using the results of the optimization of the nanohole growth, three InGaAs pseudomorphic quantum wells with nanoholes were investigated with varied depth and a constant density. A QW heterostructure without nanoholes was grown as a reference structure. For all the samples, temperature dependent Hall effect measurements, noise studies as a …
